This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Typical audio and video coding standards specify “profiles” and “levels.” A “profile” may be defined as a subset of algorithmic features of the standard and a “level” may be defined as a set of limits to the coding parameters that impose a set of constraints in decoder resource consumption. Indicated profile and level can be used to signal properties of a media stream and to signal the capability of a media decoder.
In many video coding standards the syntax structures may be arranged in different layers, where a layer may be defined as one of a set of syntactical structures in a non-branching hierarchical relationship. Generally, higher layers may contain lower layers. The coding layers may consist for example of the coded video sequence, picture, slice, and treeblock layers. Some video coding standards introduce a concept of a parameter set. An instance of a parameter set may include all picture, group of pictures (GOP), and sequence level data such as picture size, display window, optional coding modes employed, macroblock allocation map, and others. Each parameter set instance may include a unique identifier. Each slice header may include a reference to a parameter set identifier, and the parameter values of the referred parameter set may be used when decoding the slice. Parameter sets may be used to decouple the transmission and decoding order of infrequently changing picture, GOP, and sequence level data from sequence, GOP, and picture boundaries. Parameter sets can be transmitted out-of-band using a reliable transmission protocol as long as they are decoded before they are referred. If parameter sets are transmitted in-band, they can be repeated multiple times to improve error resilience compared to conventional video coding schemes. The parameter sets may be transmitted at a session set-up time. However, in some systems, mainly broadcast ones, reliable out-of-band transmission of parameter sets may not be feasible, but rather parameter sets are conveyed in-band in Parameter Set NAL units.